Fixed: dataset reading failure in case of string type

src/nxhdf5.cpp

@@ -2300,6 +2300,44 @@ public:
         }
     }
 
+
+    //--------------------------------------------------------------------------
+    std::size_t get_in_mem_data_size(hid_t dataset_id) const
+    {
+        // Get the data type of this attribute
+        H5Identifier mem_type_id = H5Dget_type(dataset_id);
+        if( !mem_type_id.is_valid() )
+            throw ImplException("H5Dget_type failed",
+                                  "nxcpp::NexusFileImpl::get_in_mem_data_size");
+
+        // Get the data type's size by first getting its native type then getting
+        // the native type's size.
+        H5Identifier native_type = H5Tget_native_type(mem_type_id, H5T_DIR_DEFAULT);
+        if( !native_type.is_valid() )
+            throw ImplException("H5Tget_native_type failed",
+                                  "nxcpp::NexusFileImpl::get_in_mem_data_size");
+
+        std::size_t type_size = H5Tget_size(native_type);
+        if (type_size == 0)
+            throw ImplException("H5Tget_size failed",
+                                  "nxcpp::NexusFileImpl::get_in_mem_data_size");
+
+        // Get number of elements of the attribute by first getting its dataspace
+        // then getting the number of elements in the dataspace
+        H5Identifier space_id = H5Dget_space(dataset_id);
+        if( !space_id.is_valid() )
+            throw ImplException("H5Aget_space failed",
+                                  "nxcpp::NexusFileImpl::get_in_mem_data_size");
+
+        hssize_t num_elements = H5Sget_simple_extent_npoints(space_id);
+        if( num_elements < 0 )
+            throw ImplException("H5Sget_simple_extent_npoints failed",
+                                  "nxcpp::NexusFileImpl::get_in_mem_data_size");
+
+        // Calculate and return the size of the data
+        return type_size * static_cast<size_t>(num_elements);
+    }
+
     //--------------------------------------------------------------------------
     void GetDataSetInfo(const std::string& name, NexusDataSetInfo* dataSetInfo)
     {
@@ -2317,22 +2355,15 @@ public:
 
             if( H5Tget_class(type_id) == H5T_STRING )
             {
-                std::string buf;
-                char *buf_p;
-
-                herr_t ret_value = H5Dread(dataset_id, type_id, space_id, H5S_ALL, H5P_DEFAULT, buf_p);
-                if( ret_value < 0 )
-                    throw ImplException("H5Dread failed", "nxcpp::NexusFileImpl::GetDataSetInfo");
-                buf = buf_p;
-                free(buf_p);
+                std::size_t size = get_in_mem_data_size(dataset_id.get());
 
                 if( 0 == rank )
                 {
-                    dataDims.push_back( (int)buf.size() );
+                    dataDims.push_back((int)size);
                     rank = 1;
                 }
                 else
-                    dataDims.front() = (int)buf.size(); // update true size
+                    dataDims.front() = (int)size; // update true size
             }
             // update nexus dataset info
             dataSetInfo->Clear();
@@ -2342,7 +2373,8 @@ public:
             dataSetInfo->SetInfo(h5Data2nexusData(type_id), rank);
             dataSetInfo->SetTotalDim(rank, dataSetInfo->DimArray());
         }
-        NEXUS_CATCH("Unable to get dataset information", "nxcpp::NexusFileImpl::GetDataSetInfo");
+        NEXUS_CATCH("Unable to get dataset information",
+                                        "nxcpp::NexusFileImpl::GetDataSetInfo");
     }
     /* CPPAPI
     void GetDataSetInfo(const std::string& name, NexusDataSetInfo* dataSetInfo)